This invention relates to an apparatus and method for implanting a conduit to allow communication of fluids from one portion of a patient""s body to another. The invention more particularly relates to a blood flow conduit implanted in a heart to allow direct flow communication between a heart chamber and a vessel and/or between two vessels. Even more particularly, the invention relates to left ventricular conduit designs and configurations, and methods for optimizing conduit designs, for controlling the flow of blood through the conduit to achieve a direct bypass of an occluded coronary artery and for optimizing total blood flow through coronary arteries with variations in proximal occlusions.
Coronary artery disease is a major problem in the U.S. and throughout the world. In fact, about 1.1 million xe2x80x9copen heartxe2x80x9d procedures are performed each year, and current estimates are that approximately 4.8 million people suffer from some degree of congestive heart failure.
When coronary arteries or other blood vessels become clogged with plaque, the results are at the very least impairment of the efficiency of the heart""s pumping action. More severe results include heart attack and/or death. In some cases, clogged arteries can be unblocked through minimally invasive techniques such as balloon angioplasty. In more difficult cases, a surgical bypass of the blocked vessel is necessary.
In a bypass operation, one or more arterial or venous segments are harvested from the body and then surgically inserted between the aorta and the coronary artery. The inserted vessel segments, or transplants, act as a bypass of the blocked portion of the coronary artery and thus provide for a free or unobstructed flow of blood to the heart. More than 500,000 bypass procedures are performed in the U.S. every year.
Coronary artery bypass grafting (CABG) has been used for more than 30 years. Initially, the saphenous vein (SV) served as the principal conduit for coronary bypass, but studies over the last dozen years have shown a 35-40% increase in 10-year patency rate or the internal thoracic artery (ITA) compared with SV. The SV, in fact, has only been shown to have a 10-year patency rate of 50%. Since the mid 1980""s, not only the ITA, but also the alternative arterial conduits have been increasingly used. These conduits include the gastroepiploic artery (GEA), inferior epigastric artery (IEA), and radial artery (RA), which have been used primarily as supplements to both the right and left ITA.
Although the use of arterial conduits results in demonstrably better long-term patency, use of arteries in place of the SV often requires complex technical challenges, such as free grafts, sequential anastomosis, and conduit-to-conduit-anastomosis. Some of the reasons for the difficulty in using arterial conduits reside in the fact that they are much more fragile than the SV and therefore easier to damage, and due to their smaller size, easier to occlude completely or partially through technical error during grafting.
Such coronary artery bypass surgery, however, is a very intrusive procedure that is expensive, time-consuming and traumatic to the patient. The operation requires an incision through the patient""s sternum (sternotomy), and the patient being placed on a bypass pump so that the heart can be operated on while not beating. A vein graft is harvested from the patient""s leg, another highly invasive procedure, and a delicate surgical procedure is required to piece the bypass graft to the coronary artery (anastomosis). Hospital stays subsequent to the surgery and convalescence periods are prolonged.
As mentioned above, another conventional treatment is percutaneous transluminal coronary angioplasty (PTCA) or other types of angioplasty. However, such vascular treatments are not always indicated due to the type or location of the blockage, or due to the risk of the emboli formation.
One bypass technique employs a stent introduced through the myocardial wall from an adjacent coronary artery to provide a direct bypass conduit between the left ventricle and the adjacent coronary artery. In one embodiment, this technique includes the delivery of a transmyocardial bypass shunt in a collapsed, reduced-profile configuration, which requires radial expansion subsequent to delivery in a bore pre-formed in the myocardial wall. The stent may extend completely through the myocardium to establish a blood flow path or conduit directly from the left ventricle to a coronary artery; downstream of a vascular obstruction or occlusion in a proximal part of the artery.
The configurations of these direct bypass conduits, which can be in the form of stents or shunts, or other similar devices, have had promising results in performing as a direct blood flow path from the left ventricle to the coronary artery. However, there is a continuing need for improved bypass methods and conduits configured to control and optimize coronary blood flow, especially to prevent or hinder loss of blood in the artery due to backflow during diastole, and for conduits that are more precisely adapted to the level of arterial occlusion experienced by a particular patient.
The advantages and purpose of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages and purpose of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
An aspect of the present invention includes a bypass conduit for implantation in a heart to bypass an at least partially occluded artery. The bypass conduit includes a first end defining a first opening and a second end opposite the first end defining a second opening. A wall extends between the first and second ends and defines a lumen extending between the first and second openings. The ends and the wall of the conduit are configured such that the conduit has a greater resistance to blood flow in a first direction than in a second direction.
Another aspect of the present invention includes a bypass conduit for implantation in a heart to bypass an at least partially occluded artery. The bypass conduit includes a first end defining a first opening and a second end opposite the first end defining a second opening. A wall extends between the first and second ends and defines a lumen extending between the first and second openings. The conduit is configured to have a greater resistance to blood flow in a first direction than in a second direction without any active flow control mechanism.
Yet another aspect of the invention includes a method of bypassing an at least partially occluded artery, comprising determining a resistance to blood flow of the artery at a location of an at least partial occlusion and selecting a conduit having a configuration based on the resistance to flow of the artery at the location of the at least partial occlusion. The method further comprises implanting the conduit in a heart wall between a heart chamber and the artery downstream of the at least partial occlusion to directly flow blood between the chamber and the artery.